N6-substituted adenosine derivatives and N6-substituted adenine derivatives are important bioactive compounds. Some of them are present as trace ingredients in plants as cytokinin to promote plant cell division and differentiation, and have important biological functions on promotion of seed germination, bud differentiation, and branch formation, as well as on production of chlorophyll and starch. In addition, they have been widely used in plant biotechnological research. Recent research shows that histidine kinases AHK2, AHK3 and AHK4 act as cytokinin receptor and play an important role in cytokinin signal transduction. Among them, research was focused on N6-isopentenyl-adenine derivaties, but less on N6-isopentenyl-adenosine. Meanwhile, due to the important physiological role, investigations were focused on antitumor and antivirus activities of these compounds, and some researchers conducted studies of N6-phenyl-adenosine derivatives, N6-phenylisopropyl-adenosine derivatives, and N6-cyclohexyl-adenosine derivatives, and activation of adenylate cyclase by these compounds through inhibiting adenosine receptor A1 and A2. However, so far, there is no experimental report of whether N6-substituted-adenosine derivatives have any sedative, hypnotic, anticonvulsant, or antiepileptic effects, or effects in treating Parkinson's disease or in prevention of dementia. See, Karel Dolezal; Igor Popa; Eva Hauserova; Lukas Spichal; Kuheli Chakrabarty; Ondrej Novak; Vladimir Krystof; Jiri Voller; Jan Holub and Miroslav Strnad, Preparation, biological activity and endogenous occurrence of N6-benzyladenosines, Bioorganic & Medicinal Chemistry, 2007, 15, 3737-3747 (as well as the references in this article); Substitution Derivatives of N6-benzyladenosine, Methods of Their Preparation, Their Use for Preparation of Drugs, Cosmetic Preparations and Growth Regulations Containing This Compounds, WO 2004/058791 A2, 15 Jul. 2004; Madan M. Kwatra; Edward Leung; M. Marlene Hosey, Richrad D. Dreen, N6-phenyladenosines: Pronounced Effect of Phenyl Substituents on Affinity for A2 Adenosine Receptors, 1987, 30, 954-956 (as well as the references in this article).
Recently, N6-(4-hydroxybenzyl)-adenosine was reported from Rhizoma Gastrodiae, and was found to be effective in preventing PC12 cell apoptosis and binding to adenosine A2A receptor. However, there is no report of whether this compound and its analogues have any sedative and hypnotic effects in the central nervous and mental systems. Nai-Kuei Huang, Yijuang Chem, Jim-Min Fang, Chia-I Lin, Wang-Ping Chen, and Yun-Lian Lin, Neuroprotective Principles from Gastrodia elata, J. Nat. Prod., 2007, 70, 571-574 (references cited therein).
